1. Field of the Invention
This invention relates to a nuclear reactor fuel element which consists of a multiplicity of fuel rods, disposed or held in spaced relation by spacers arranged in several planes, and fastened to at least one support plate. Each fuel rod has a tubular casing which contains the nuclear fuel, for instance, in the form of pellets. Next to the fuel rods, these spacers constitute the most essential structural units within the fuel elements because by means of these spacers the fuel rods are maintained in a predetermined spacial relation. This is necessary so that over the entire life of the nuclear reactor, a completely uniform cooling of the fuel rods and the fuel elements is achieved by the reactor coolant. The reactor coolant may be either a gas or a liquid.
2. Description of the Prior Art
It is known that spacers automatically interact with the fuel rods and the latter, in turn, interact with the tubular casings. For this reason, the type of material and the wall thicknesses of the parts in contact with each other must be matched to each other, taking into consideration the mechanical forces which may occur. Thus, the wall thicknesses of the tubular casing should be so large that mechanical damage to the tubular casings cannot occur. On the other hand, the total amount of structural material within the active zones of the reactor core should be kept as low as possible for reasons of neutron efficiency. In addition, the problems of heat removal and creep at the operating temperature of the reactor are important considerations.